1. Field of the Invention
This invention relates to a method of causing an observer to get a three-dimensional impression of a scene from a two-dimensional representation thereof, in which the observer's movements are monitored and means are provided by which, depending on these movements, two-dimensional representations uniquely associated with each body position of the observer are displayed on a screen.
Description of the Related Art
A similar method is known for training a driver by means of visual simulation to manoeuvre a vehicle correctly to a pre-determined position. According to the known prior method, part of the portion of the vehicle which the driver has in view during manoeuvring is recorded by means of a first camera. This portion may be of both two-dimensional and three-dimensional design. By means of a second camera, a picture is taken of a three-dimensional design of a scene representing surroundings with the position into which the vehicle is to be manoeuvred. The images from the first and second cameras are combined and supplied to a projector, which projects this combined image onto a screen. The combination of the two images is so effected that movements of the driver result in such changes in the reproduction of the image of the first camera in the projected image that it seems as if the driver is actually within or on the vehicle. At the same time, in depicting the image of the second camera, the commands given by the driver for manoeuvring the vehicle to the pre-determined position are taken into account.
It is true that the prior method permits making good distance estimates between, for example, the leading edge of the vehicle and the position into which it must be manoeuvred, but it is not possible to accurately estimate the depth between the various objects present in the scene recorded by the second camera.
The wish of having two-dimensional pictures on a projection screen or on a display screen create a three-dimensional impression with an observer has existed for quite some time. To realize this, various solutions have been proposed, which each have their own specific disadvantages.
According to a first solution principle, use is made of the so-called binocular disparity. As a human being has two eyes, whose pupils are, on average, 6.5 cm apart, the left-hand retinal image is not exactly equal to the right-hand retinal image. When an object is viewed, the two retinal images together give a three-dimensional picture of the object, with the depth observed corresponding to the degree of disparity.
Most of the three-dimensional image systems are based on the presentation of a separate left-hand and right-hand image, which images are combined to form one spatial image. This combination can be effected either by means of special glasses, such as stereoscopic, anaglyphic, polarisation, or light ports glasses, or in the image proper by means of a stereoscopic lens system arranged on the screen.
In all these solutions based on binocular disparity, a moderate to fair depth impression is formed, but the observer often gets an annoying headache after some time. Moreover, either special glasses are required or an expensive adaptation of the imaging system.
A second solution principle, the so-called triangle system, is based on the fact that the convergence of our eyes gives us distance information. The depth impression obtained by means of this principle is rather weak, while in addition special glasses are required.
A third solution principle is based on the formation of a virtual volume. There are two distinct systems, namely, the varifocal mirror system and holography, in which a virtual three-dimensional image is formed in different manners.
In a varifocal mirror system this is effected by projecting a two-dimensional image on an accurately controlled vibrating mirror. An image which on a normal mirror would be a circle becomes a tube on such a vibrating mirror. The image gets a virtual added dimension.
In holography the virtual volume is formed by recording optical interference patterns on a special photographic plate which, with suitable lighting, also give the impression of a virtual volume.
As the technical procedures in both the varifocal mirror system and holography are rather complicated, it has hitherto to only being possible to use these for depicting non-moving objects or scenes. Both systems do produce a good depth impression.
All of the methods described above, in which a good three-dimensional impression is obtained from a twodimensional image are limited either owing to the fact that the realisation of the system is expensive, or because a reproduction of still pictures is possible only. The simpler systems, such as the anaglyphic system, which can also be used in television broadcasts, only a moderate depth effect is obtained, while the viewer must wear special glasses of different colors, and will get a headache after a short time. In addition color reproduction is difficult, and there is only a depth effect from one point of view.